Mast cells and COPD

Meta-analysis of single-cell RNA-sequencing data for depicting the transcriptomic landscape of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a respiratory disease characterized by airflow limitation and chronic inflammation of the lungs that is a leading cause of death worldwide. Since the complete pathological mechanisms at the single-cell level are not fully understood yet, an integrative approach to characterizing the single-cell-resolution landscape of COPD is required. To identify the cell types and mechanisms associated with the development of COPD, we conducted a meta-analysis using three single-cell RNA-sequencing datasets of COPD. Among the 154,011 cells from 16 COPD patients and 18 healthy subjects, 17 distinct cell types were observed. Of the 17 cell types, monocytes, mast cells, and alveolar type 2 cells (AT2 cells) were found to be etiologically implicated in COPD based on genetic and transcriptomic features. The most transcriptomically diversified states of the three etiological cell types showed significant enrichment in immune/inflammatory responses (monocytes and mast cells) and/or mitochondrial dysfunction (monocytes and AT2 cells). We then identified three chemical candidates that may potentially induce COPD by modulating gene expression patterns in the three etiological cell types. Overall, our study suggests the single-cell level mechanisms underlying the pathogenesis of COPD and may provide information on toxic compounds that could be potential risk factors for COPD.

TLR7 promotes smoke-induced experimental lung damage through the activity of mast cell tryptase

Toll-like receptor 7 (TLR7) is known for eliciting immunity against single-stranded RNA viruses, and is increased in both human and cigarette smoke (CS)-induced, experimental chronic obstructive pulmonary disease (COPD). Here we show that the severity of CS-induced emphysema and COPD is reduced in TLR7-deficient mice, while inhalation of imiquimod, a TLR7-agonist, induces emphysema without CS exposure. This imiquimod-induced emphysema is reduced in mice deficient in mast cell protease-6, or when wild-type mice are treated with the mast cell stabilizer, cromolyn. Furthermore, therapeutic treatment with anti-TLR7 monoclonal antibody suppresses CS-induced emphysema, experimental COPD and accumulation of pulmonary mast cells in mice. Lastly, TLR7 mRNA is increased in pre-existing datasets from patients with COPD, while TLR7+ mast cells are increased in COPD lungs and associated with severity of COPD. Our results thus support roles for TLR7 in mediating emphysema and COPD through mast cell activity, and may implicate TLR7 as a potential therapeutic target.

Screening and identification of tissue-infiltrating immune cells and genes for patients with emphysema phenotype of COPD

Objective

To study the tissue-infiltrating immune cells of the emphysema phenotype of chronic obstructive pulmonary disease (COPD) and find the molecular mechanism related to the development of emphysema to offer potential targets for more precise treatment of patients with COPD.

Methods

Combined analyses of COPD emphysema phenotype lung tissue-related datasets, GSE47460 and GSE1122, were performed. CIBERSORT was used to assess the distribution of tissue-infiltrating immune cells. Weighted gene co-expression network analysis (WGCNA) was used to select immune key genes closely related to clinical features. Rt-qPCR experiments were used for the validation of key genes. Emphysema risk prediction models were constructed by logistic regression analysis and a nomogram was developed.

Results

In this study, three immune cells significantly associated with clinical features of emphysema (FEV1 post-bronchodilator % predicted, GOLD Stage, and DLCO) were found. The proportion of neutrophils (p=0.025) infiltrating in the emphysema phenotype was significantly increased compared with the non-emphysema phenotype, while the proportions of M2 macrophages (p=0.004) and resting mast cells (p=0.01) were significantly decreased. Five immune-related differentially expressed genes (DEGs) were found. WGCNA and clinical lung tissue validation of patients with emphysema phenotype were performed to further screen immune-related genes closely related to clinical features. A key gene (SERPINA3) was selected and included in the emphysema risk prediction model. Compared with the traditional clinical prediction model (AUC=0.923), the combined prediction model, including SERPINA3 and resting mast cells (AUC=0.941), had better discrimination power and higher net benefit.

Conclusion

This study comprehensively analyzed the tissue-infiltrating immune cells significantly associated with emphysema phenotype, including M2 macrophages, neutrophils, and resting mast cells, and identified SERPINA3 as a key immune-related gene.

Identification of Ferroptosis-Related Hub Genes and Their Association with Immune Infiltration in Chronic Obstructive Pulmonary Disease by Bioinformatics Analysis

Purpose

Ferroptosis and immune infiltration are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). We aim to identify ferroptosis-related hub genes and analyze their association with immune infiltration in COPD through bioinformatics methods.

Materials and Methods

The mRNA microarray data of GSE38974 were downloaded from Gene Expression Omnibus to obtain differentially expressed genes (DEGs). The DEGs were intersected with ferroptosis-related genes (FRGs) from FerrDb to obtain differentially expressed FRGs. GO and KEGG enrichment and protein–protein interaction (PPI) analyses of differentially expressed FRGs were conducted in R software and STRING database. The key module and hub genes were screened by Cytoscape software. MiRNAs, transcription factors and signal molecules were predicted in miRNet and NetworkAnalyst. The disease correlation in the Comparative Toxicomics Database (CTD) and the receiver operating characteristic (ROC) curves of hub genes were analyzed. Immune infiltration was evaluated by CIBERSORT algorithm. Spearman correlation analyses were conducted between hub genes and differentially infiltrated immune cells.

Results

Fifteen differentially expressed FRGs were identified, which were enriched in some terms involving airway inflammatory responses and structural remodeling. Five hub genes were selected including HIF1A, IL6, PTGS2, CDKN1A and ATM. Inference scores in CTD indicated their association with COPD. Two miRNAs, five transcription factors and one signal molecule were predicted. The combination of hub genes could be a fine diagnostic indicator of COPD (AUC: 0.981, CI: 0.940-1.000). Immune infiltration evaluation showed that monocytes and M0 macrophages were upregulated in COPD lung tissues, while CD8 T cells, activated NK cells, M2 macrophages, resting dendritic cells and resting mast cells were downregulated. The hub genes were significantly associated with differentially infiltrated immune cells.

Conclusion

We identified five ferroptosis-related hub genes (HIF1A, IL6, PTGS2, CDKN1A and ATM) in COPD, and found that they may influence the pathogenesis of COPD by regulating ferroptosis and thus affecting infiltrating immune cells.

The inhibitor miR-21 regulates macrophage polarization in an experimental model of chronic obstructive pulmonary disease

INTRODUCTION

In chronic obstructive pulmonary disease (COPD), macrophages play an indispensable role. In the lung tissues of COPD patients and smokers, macrophages can be observed to polarize towards M2 phenotype. The molecular mechanism of this process is unclear, and it has not been fully elucidated in COPD.

METHODS

We bought laboratory animals [C57BL/6 and miR-21^-/- C57BL/6(F1)] from the Jackson Laboratory. The model of COPD mice was established by cigarette smoke (CS) exposure combined with intraperitoneal injection of cigarette smoke extract (CSE). RT-PCR detected the expression levels of inflammatory factors and markers associated with M1 and M2 macrophages. The ratio of M2 macrophages to M1 macrophages was detected by immunohistochemical staining.

RESULTS

The level of miR-21 was increased in RAW264.7 cells intervened by CSE and in lung tissue and bone marrow-derived macrophages (BMDMs) from COPD mice. CSE can gradually over time increase the level of miR-21. The proportion of M2 macrophages to M1 macrophages had a positive correlation with miR-21. Knockdowning miR-21 can reduce lung tissue damage. CSE also increased the levels of related inflammatory factors and markers associated with M2 macrophages, and an miR-21 inhibitor can reverse this conversion.

CONCLUSIONS

We confirmed that CSE can lead to macrophage transformation to the M2 phenotype and an increase in the expression level of miR-21. Knockdown of the miR-21 gene could inhibit the transformation of macrophages to the M2 phenotype in COPD.

Aloe-emodin, a naturally occurring anthraquinone, is a highly potent mast cell stabilizer through activating mitochondrial calcium uniporter

Mast cells play a fundamental role in immune system. Upon stimulation, they are activated via IgE dependent or independent pathway and then release granules which contain plenty of preformed constituents. Mast cell stabilizers are commonly used clinically for inhibiting the degranulation of mast cells. In the current study, we firstly identified aloe-emodin, a naturally occurring anthraquinone, was a prominent mast cell stabilizer. It could strikingly dampen IgE/FcεRI- and MAS-related G protein coupled receptor (Mrgpr)-mediated mast cell degranulation in vitro and in vivo. Mechanism study indicated that aloe-emodin rapidly and reversibly decreased cytosolic Ca²⁺ (Ca²⁺_[c]) concentration through enhancing the mitochondrial Ca²⁺ (Ca²⁺_[m]) uptake. After genetically silencing or pharmacologic inhibiting mitochondrial calcium uniporter (MCU), the effects of aloe-emodin on the Ca²⁺_[c] level and mast cell degranulation were significantly weakened. In contrast to six clinical drugs with mast cell stabilizing properties (amlexanox, tranilast, ketotifen, cromolyn disodium salt, dexamethasone and pimecrolimus), aloe-emodin showed an impressive and potent inhibitory action on the mast cell degranulation. Collectively, aloe-emodin is a highly potent mast cell stabilizer. By directly activating MCU, it decreases Ca²⁺_[c] level to suppress mast cell degranulation. Our study may provide a promising candidate for the treatment of mast cell activation-related diseases.

HIV gp120 Induces the Release of Proinflammatory, Angiogenic, and Lymphangiogenic Factors from Human Lung Mast Cells

Human lung mast cells (HLMCs) express the high-affinity receptor FcεRI for IgE and are involved in chronic pulmonary diseases occurring at high frequency among HIV-infected individuals. Immunoglobulin superantigens bind to the variable regions of either the heavy or light chain of immunoglobulins (Igs). Glycoprotein 120 (gp120) of HIV-1 is a typical immunoglobulin superantigen interacting with the heavy chain, variable 3 (V_H3) region of human Igs. The present study investigated whether immunoglobulin superantigen gp120 caused the release of different classes of proinflammatory and immunoregulatory mediators from HLMCs. The results show that gp120 from different clades induced the rapid (30 min) release of preformed mediators (histamine and tryptase) from HLMCs. gp120 also caused the de novo synthesis of cysteinyl leukotriene C₄ (LTC₄) and prostaglandin D₂ (PGD₂) from HLMCs. Incubation (6 h) of HLMC with gp120 induced the release of angiogenic (VEGF-A) and lymphangiogenic (VEGF-C) factors from HLMCs. The activating property of gp120 was mediated through the interaction with IgE V_H3⁺ bound to FcεRI. Our data indicate that HIV gp120 is a viral superantigen, which induces the release of different proinflammatory, angiogenic, and lymphangiogenic factors from HLMCs. These observations could contribute to understanding, at least in part, the pathophysiology of chronic pulmonary diseases in HIV-infected individuals.

How Do Innate Immune Cells Contribute to Airway Remodeling in COPD Progression?

Recently, the therapeutic potential of immune-modulation during the progression of chronic obstructive pulmonary disease (COPD) has been attracting increasing interest. However, chronic inflammatory response has been over-simplified in descriptions of the mechanism of COPD progression. As a form of first-line airway defense, epithelial cells exhibit phenotypic alteration, and participate in epithelial layer disorganization, mucus hypersecretion, and extracellular matrix deposition. Dendritic cells (DCs) exhibit attenuated antigen-presenting capacity in patients with advanced COPD. Immature DCs migrate into small airways, where they promote a pro-inflammatory microenvironment and bacterial colonization. In response to damage-associated molecular patterns (DAMPs) in lung tissue affected by COPD, neutrophils are excessively recruited and activated, where they promote a proteolytic microenvironment and fibrotic repair in small airways. Macrophages exhibit decreased phagocytosis in the large airways, while they demonstrate high pro-inflammatory potential in the small airways, and mediate alveolar destruction and chronic airway inflammation. Natural killer T (NKT) cells, eosinophils, and mast cells also play supplementary roles in COPD progression; however, their cellular activities are not yet entirely clear. Overall, during COPD progression, “exhausted” innate immune responses can be observed in the large airways. On the other hand, the innate immune response is enhanced in the small airways. Approaches that inhibit the inflammatory cascade, chemotaxis, or the activation of inflammatory cells could possibly delay the progression of airway remodeling in COPD, and may thus have potential clinical significance.

Type 2 innate lymphoid cells participate in IL-33-stimulated Th2-associated immune response in chronic obstructive pulmonary disease

The aim of the present study was to investigate the roles of type 2 innate lymphoid cells (ILC2s) and interleukin-33 (IL-33) in chronic obstructive pulmonary disease (COPD). Serum and peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls and COPD patients. ILC2 cells from the peripheral blood of COPD patients were stimulated with IL-33 or neutralizing ST2 antibody+IL-33 in vitro. The cell viability was assessed using a Cell Counting Kit-8 assay. ELISA was used to detect serum IL-33 and the levels of IL-4, IL-5, IL-6, IL-13 and soluble ST2 (sST2) in the culture supernatant. The percentage of ILC2 cells was measured by flow cytometry. The mRNA expression levels of GATA binding protein 3 (GATA3), RAR-related orphan receptor (ROR)α, ST2 and prostaglandin D2 receptor 2 (CRTH2) were detected by reverse transcription-quantitative PCR. It was revealed that IL-33, IL-5, IL-6 and IL-13 were significantly elevated in peripheral blood of patients with COPD. The proportion of ILC2s in peripheral blood of COPD patients was significantly increased, and the expression of RORA and CRTH2 was increased. The proportion of ST2⁺ ILC2 cells was significantly increased. After 48 h of IL-33 stimulation in vitro, the ratio of linage^-CD45⁺CD127⁺CRTH2⁺ cells reached a maximum. In addition, the viability of ILC2 cells, the expression levels of RORA, GATA3, ST2 and CRTH2 mRNA and the cytokines IL-4, IL-6, IL-5, IL-13 and sST2 were significantly increased. These effects were abrogated by treatment with anti-ST2. In conclusion, IL-33 is upregulated in the serum of patients with COPD and the proportion of ILC2s among the PBMCs is increased. IL-33 may promote the proliferation of ILC2 cells and secrete type 2 T-helper cell cytokines to participate in the immune response in COPD.

Protein carbonylation in human bronchial epithelial cells exposed to cigarette smoke extract

Cigarette smoke is a well-established exogenous risk factor containing toxic reactive molecules able to induce oxidative stress, which in turn contributes to smoking-related diseases, including cardiovascular, pulmonary, and oral cavity diseases. We investigated the effects of cigarette smoke extract on human bronchial epithelial cells. Cells were exposed to various concentrations (2.5-5-10-20%) of cigarette smoke extract for 1, 3, and 24 h. Carbonylation was assessed by 2,4-dinitrophenylhydrazine using both immunocytochemical and Western immunoblotting assays. Cigarette smoke induced increasing protein carbonylation in a concentration-dependent manner. The main carbonylated proteins were identified by means of two-dimensional electrophoresis coupled to MALDI-TOF mass spectrometry analysis and database search (redox proteomics). We demonstrated that exposure of bronchial cells to cigarette smoke extract induces carbonylation of a large number of proteins distributed throughout the cell. Proteins undergoing carbonylation are involved in primary metabolic processes, such as protein and lipid metabolism and metabolite and energy production as well as in fundamental cellular processes, such as cell cycle and chromosome segregation, thus confirming that reactive carbonyl species contained in cigarette smoke markedly alter cell homeostasis and functions.

Role of inflammatory cells in airway remodeling in COPD

COPD is characterized by chronic bronchitis, chronic airway obstruction, and emphysema, leading to a progressive and irreversible decline in lung function. Inflammation is central for the development of COPD. Chronic inflammation in COPD mainly involves the infiltration of neutrophils, macrophages, lymphocytes, and other inflammatory cells into the small airways. The contribution of resident airway structural cells to the inflammatory process is also important in COPD. Airway remodeling consists of detrimental changes in structural tissues and cells including airway wall thickening, epithelial metaplasia, goblet cell hypertrophy, and smooth muscle hyperplasia. Persistent airway inflammation might contribute to airway remodeling and small airway obstruction. However, the underlying mechanisms remain unclear. In this review, we will provide an overview of recent insights into the role of major immunoinflammatory cells in COPD airway remodeling.

Mast cells and mast cell tryptase enhance migration of human lung fibroblasts through protease-activated receptor 2

BACKGROUND

Mast cells may activate fibroblasts and contribute to remodeling processes in the lung. However, the mechanism behind these actions needs to be further investigated. Fibroblasts are major regulators of on-going remodeling processes. Protease activated receptor 2 (PAR2) expressed by fibroblasts may be activated by serine proteases, such as the mast cell mediator tryptase. The objective in this study was to investigate the effects of mast cells and specifically mast cell tryptase on fibroblast migration and the role of PAR2 activation.

METHODS

Human lung fibroblasts (HFL-1) were cultured together with human peripheral blood-derived mast cells or LAD2 mast cells and stimulated with either conditioned medium from LAD2 cells or tryptase. Analyses of immunological stimulation of mast cells by IgE/anti IgE in the co-culture system were also performed. The importance of PAR2 activation by mast cells and mast cell tryptase for the migratory effects of fibroblasts was investigated by pre-treatment with the PAR2 antagonist P2pal-18S. The expression of PAR2 was analyzed on fibroblasts and mast cells.

RESULTS

The migratory capacity of HFL-1 cells was enhanced by blood-derived mast cells (p < 0.02), LAD2 cells (p < 0.001), conditioned medium (p < 0.05) and tryptase (p < 0.006). P2pal-18S decreased the induced migration caused by mast cells (p < 0.001) and tryptase (p < 0.001) and the expression of PAR2 was verified in HFL-1 cells. Mast cells immunologically stimulated with IgE/Anti IgE had no further effects on fibroblast migration.

CONCLUSIONS

Mast cells and the mast cell mediator tryptase may have crucial roles in inducing lung fibroblast migration via PAR-2 activation, which may contribute to remodeling processes in chronic lung diseases.

Role of mast cells in bronchial contraction in nonallergic obstructive lung pathology

The role of mast cells in contractile bronchial smooth muscle activity has been evaluated in a model of chronic obstructive pulmonary disease induced in rats that were intermittently exposed to nitrogen dioxide (NO₂) for 60 days. Starting from the 31st day, one group of rats inhaled sodium cromoglycate before exposure to NO₂ to stabilize mast cell membranes. The second group (control) was not treated. Isometric smooth muscle contraction was analysed in isolated bronchial samples in response to nerve and smooth muscle stimulation. Histological analysis revealed large numbers of mast cells in lung tissue of COPD model rats. The inhibition of mast cell degranulation by sodium cromoglycate prevented the development of nerve-stimulated bronchial smooth muscle hyperactivity in COPD model rats. Histamine or adenosine-induced hyperactivity on nerve stimulation was also inhibited by sodium cromoglycate in bronchial smooth muscle in both control and COPD model rats. This suggests that the mechanism of contractile activity enhancement of bronchial wall smooth muscle cells may be mediated through the activation of resident mast cells transmembrane adenosine receptors resulting in their partial degranulation, with the released histamine acting upon histamine H1-receptors which trigger reflex pathways via intramural ganglion neurons.

The Three-Herb Formula Shuang-Huang-Lian stabilizes mast cells through activation of mitochondrial calcium uniporter

Mast cells (MCs) are key effector cells of IgE-FcεRI- or MrgprX2-mediated signaling event. Shuang-Huang-Lian (SHL), a herbal formula from Chinese Pharmacopoeia, has been clinically used in type I hypersensitivity. Our previous study demonstrated that SHL exerted a non-negligible effect on MC stabilization. Herein, we sought to elucidate the molecular mechanisms of the prominent anti-allergic ability of SHL. MrgprX2- and IgE-FcεRI-mediated MC activation in vitro and in vivo models were developed by using compound 48/80 (C48/80) and shrimp tropomyosin (ST), respectively. Our data showed that SHL markedly dampened C48/80- or ST-induced MC degranulation in vitro and in vivo. Mechanistic study indicated that cytosolic Ca²⁺ (Ca²⁺_[c]) level decreased rapidly and sustainably after SHL treatment, and then returned to homeostasis when SHL was withdrawn. Moreover, SHL decreases Ca²⁺_[c] levels mainly through enhancing the mitochondrial Ca²⁺ (Ca²⁺_[m]) uptake. After genetically silencing or pharmacologic inhibiting mitochondrial calcium uniporter (MCU), the effect of SHL on the Ca²⁺_[c] level and MC degranulation was significantly weakened. Simultaneously, the activation of SHL on Ca²⁺_[m] uptake was completely lost. Collectively, by activating MCU, SHL decreases Ca²⁺_[c] level to stabilize MCs, thus exerting a remarkable anti-allergic activity, which could have considerable influences on clinical practice and research.

Cigarette smoke extract-treated mast cells promote alveolar macrophage infiltration and polarization in experimental chronic obstructive pulmonary disease

OBJECTIVE

Cigarette smoking is the main cause of chronic obstructive pulmonary disease (COPD) and may modulate the immune response of exposed individuals. Mast cell function can be altered by cigarette smoking, but the role of smoking in COPD remains poorly understood. The current study aimed to explore the role of cigarette smoke extract (CSE)-treated mast cells in COPD pathogenesis.

METHODS

Cytokine and chemokine expression as well as degranulation of bone marrow-derived mast cells (BMMCs) were detected in cells exposed to immunoglobulin E (IgE) and various doses of CSE. Adoptive transfer of CSE-treated BMMCs into C57BL/6J mice was performed, and macrophage infiltration and polarization were evaluated by fluorescence-activated cell sorting (FACS). Furthermore, a coculture system of BMMCs and macrophages was established to examine macrophage phenotype transition. The role of protease serine member S31 (Prss31) was also investigated in the co-culture system and in COPD mice.

RESULTS

CSE exposure suppressed cytokine expression and degranulation in BMMCs, but promoted the expressions of chemokines and Prss31. Adoptive transfer of CSE-treated BMMCs induced macrophage infiltration and M2 polarization in the mouse lung. Moreover, CSE-treated BMMCs triggered macrophage M2 polarization via Prss31 secretion. Recombinant Prss31 was shown to activate interleukin (IL)-13/IL-13Rα/Signal transducers and activators of transcription (Stat) 6 signaling in macrophages. Additionally, a positive correlation was found between Prss31 expression and the number of M2 macrophages in COPD mice.

CONCLUSION

In conclusion, CSE-treated mast cells may induce macrophage infiltration and M2 polarization via Prss31 expression, and potentially contribute to COPD progression.

Protection from Cigarette Smoke-Induced Lung Dysfunction and Damage by H2 Relaxin (Serelaxin)

Cigarette smoke (CS) is the major etiologic factor of chronic obstructive pulmonary disease (COPD), which is characterized by airway remodeling, lung inflammation and fibrosis, emphysema, and respiratory failure. The current therapies can improve COPD management but cannot arrest its progression and reduce mortality. Hence, there is a major interest in identifying molecules susceptible of development into new drugs to prevent or reduce CS-induced lung injury. Serelaxin (RLX), or recombinant human relaxin-2, is a promising candidate because of its anti-inflammatory and antifibrotic properties highlighted in lung disease models. Here, we used a guinea pig model of CS-induced lung inflammation, and remodeling reproducing some of the hallmarks of COPD. Animals exposed chronically to CS (8 weeks) were treated with vehicle or RLX, delivered by osmotic pumps (1 or 10 μg/day) or aerosol (10 μg/ml/day) during CS treatment. Controls were nonsmoking animals. RLX maintained airway compliance to a control-like pattern, likely because of its capability to counteract lung inflammation and bronchial remodeling. In fact, treatment of CS-exposed animals with RLX reduced the inflammatory recruitment of leukocytes, accompanied by a significant reduction of the release of proinflammatory cytokines (tumor necrosis factor α and interleukin-1β). Moreover, RLX was able to counteract the adverse bronchial remodeling and emphysema induced by CS exposure by reducing goblet cell hyperplasia, smooth muscle thickening, and fibrosis. Of note, RLX delivered by aerosol has shown a comparable efficacy to systemic administration in reducing CS-induced lung dysfunction and damage. In conclusion, RLX emerges as a new molecule to counteract CS-induced inflammatory lung diseases.

[Morphometric characteristics of the bronchial tree in smokers with and without chronic obstructive pulmonary disease]

AIM

To reveal the tissue, cellular, and molecular predictors leading to the development of chronic obstructive pulmonary disease (COPD) in smokers on the basis of a morphometric analysis of bronchial biopsy specimens.

MATERIALS AND METHODS

A cross-sectional study was conducted in 115 smokers aged 40 to 60 years (58.3±3.24 years) with a male predominance of 90.9%. Morphological examination of bronchial biopsy specimens was first made in the smoking patients with and without COPD.

RESULTS

The smokers with COPD versus those without this condition were found to have a statistically significant increase in a number of indicators: the specific volume (SV) of the surface epithelium (p=0.017), SV of basal epitheliocytes (p=0.008), the height of the epithelium (p=0.001), and the thickness of the basal membrane (p=0.006) due to impaired regeneration processes in the bronchial epithelium and to fibrosis of the lamina propria of the bronchi with a concurrent increase in the total number of fibroblasts. The group of smokers with COPD, unlike the comparison group, showed signs of vascular remodeling and microcirculatory disorders as the increased connective tissue volumetric density of the lamina propria of the bronchi with predominant perivascular localization. This was followed by reductions in the relative volume of capillaries (p=0.016), in the SV of micropinocytic vesicles (p=0.005), and the size of Weibel-Palade bodies (p=0.004) in the endotheliocytes. In the COPD patients, the total density of cell infiltrate per mm2 of the lamina propria of the bronchi was statistically significantly (p<0.001) greater than that in the comparison group at the expense of neutrophils, lowly and moderately granulated basophils, macrophages, plasma cells with a simultaneous rise in their interepithelial forms.

CONCLUSION

Compensatory structural changes without signs of bronchial wall remodeling were recorded in the smokers without signs of bronchial disease. The smokers with the examined nosological entity were observed to have morphological signs of hemodynamic disorders, as well as perivascular fibrosis, atrophy, and squamous cell metaplasia of the bronchial epithelial lining.

Potential roles of telocytes in lung diseases

Telocytes (TCs) are a unique type of interstitial cells with specific, extremely long prolongations named telopodes (Tps), as shown by immune-positive staining against CD34, c-kit and vimentin. They were found in many organs of mammals, with potential biological functions, including the trachea and lung, even though the exact function remains unclear. Here, we give a historical overview of the TCs research field and summarize the latest findings associated with TCs, with a special focus on the recent progress about TCs specific gene and protein profiles that has been made in understanding that TCs may play a potential, but important, role in the pathogenesis of lung diseases.

A 7-month cigarette smoke inhalation study in C57BL/6 mice demonstrates reduced lung inflammation and emphysema following smoking cessation or aerosol exposure from a prototypic modified risk tobacco product

Modified risk tobacco products (MRTP) are designed to reduce smoking-related health risks. A murine model of chronic obstructive pulmonary disease (COPD) was applied to investigate classical toxicology end points plus systems toxicology (transcriptomics and proteomics). C57BL/6 mice were exposed to conventional cigarette smoke (3R4F), fresh air (sham), or a prototypic MRTP (pMRTP) aerosol for up to 7 months, including a cessation group and a switching-to-pMRTP group (2 months of 3R4F exposure followed by fresh air or pMRTP for up to 5 months respectively). 3R4F smoke induced the typical adaptive changes in the airways, as well as inflammation in the lung, associated with emphysematous changes (impaired pulmonary function and alveolar damage). At nicotine-matched exposure concentrations of pMRTP aerosol, no signs of lung inflammation and emphysema were observed. Both the cessation and switching groups showed a similar reversal of inflammatory responses and no progression of initial emphysematous changes. A significant impact on biological processes, including COPD-related inflammation, apoptosis, and proliferation, was identified in 3R4F-exposed, but not in pMRTP-exposed lungs. Smoking cessation or switching reduced these perturbations to near sham-exposed levels. In conclusion, the mouse model indicated retarded disease progression upon cessation or switching to pMRTP which alone had no adverse effects.

Pneumocystis jirovecii colonization in Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is associated with a chronic inflammatory response in airways and lung parenchyma that results in significant morbidity and mortality worldwide. Cigarette smoking considered as an important risk factor plays a role in pathogenesis of disease. Pneumocystis jirovecii is an atypical opportunistic fungus that causes pneumonia in immunosuppressed host, although the low levels of its DNA in patients without signs and symptoms of pneumonia, which likely represents colonization. The increased prevalence of P. jirovecii colonization in COPD patients has led to an interest in understanding its role in the disease. P. jirovecii colonization in these patients could represent a problem for public health since colonized patients could act as a major reservoir and source of infection for susceptible subjects. Using sensitive molecular techniques, low levels of P. jirovecii DNA have been detected in the respiratory tract of certain individuals. It is necessary to elucidate the role of P. jirovecii colonization in the natural history of COPD patients in order to improve the clinical management of this disease. In the current review paper, we discuss P. jirovecii colonization in COPD patients.

Risk loci for chronic obstructive pulmonary disease: a genome-wide association study and meta-analysis

BACKGROUND

The genetic risk factors for susceptibility to chronic obstructive pulmonary disease (COPD) are still largely unknown. Additional genetic variants are likely to be identified by genome-wide association studies in larger cohorts or specific subgroups. We sought to identify risk loci for moderate to severe and severe COPD with data from several cohort studies.

METHODS

We combined genome-wide association analysis data from participants in the COPDGene study (non-Hispanic white and African-American ethnic origin) and the ECLIPSE, NETT/NAS, and Norway GenKOLS studies (self-described white ethnic origin). We did analyses comparing control individuals with individuals with moderate to severe COPD and with a subset of individuals with severe COPD. Single nucleotide polymorphisms yielding a p value of less than 5 × 10(-7) in the meta-analysis at loci not previously described were genotyped in individuals from the family-based ICGN study. We combined results in a joint meta-analysis (threshold for significance p<5 × 10(-8)).

FINDINGS

Analysis of 6633 individuals with moderate to severe COPD and 5704 control individuals confirmed association at three known loci: CHRNA3 (p=6·38 × 10(-14)), FAM13A (p=1·12 × 10(-14)), and HHIP (p=1·57 × 10(-12)). We also showed significant evidence of association at a novel locus near RIN3 (p=5·25 × 10(-9)). In the overall meta-analysis (ie, including data from 2859 ICGN participants), the association with RIN3 remained significant (p=5·4 × 10(-9)). 3497 individuals were included in our analysis of severe COPD. The effect estimates for the loci near HHIP and CHRNA3 were significantly stronger in severe disease than in moderate to severe disease (p<0·01). We also identified associations at two additional loci: MMP12 (overall joint meta-analysis p=2·6 × 10(-9)) and TGFB2 (overall joint meta-analysis p=8·3 × 10(-9)).

INTERPRETATION

We have confirmed associations with COPD at three known loci and identified three new genome-wide significant associations. Genetic variants other than in α-1 antitrypsin increase the risk of COPD.

FUNDING

US National Heart, Lung, and Blood Institute; the Alpha-1 Foundation; the COPD Foundation through contributions from AstraZeneca, Boehringer Ingelheim, Novartis, and Sepracor; GlaxoSmithKline; Centers for Medicare and Medicaid Services; Agency for Healthcare Research and Quality; and US Department of Veterans Affairs.

CRAC channel inhibition produces greater anti-inflammatory effects than glucocorticoids in CD8 cells from COPD patients

There are increased numbers of pulmonary CD8 lymphocytes in COPD (chronic obstructive pulmonary disease). CRAC (calcium release-activation calcium) channels play a central role in lymphocyte activation though the regulation of the transcription factor NFAT (nuclear factor of activated T-cells). We studied the expression of NFAT in lungs from COPD patients compared with controls, and evaluated the effects of CRAC channel inhibition compared with corticosteroids on NFAT activation and cytokine production in CD8 cells from COPD patients. The effects of the corticosteroid dexamethasone, the calcineurin inhibitor cyclosporin and the CRAC channel inhibitor Synta 66 were studied on cytokine production and NFAT activation using peripheral blood and isolated pulmonary CD8 cells. NFAT1 and CD8 co-expression in the lungs was compared in COPD patients and controls using combined immunohistochemistry and immunofluorescence. NFAT inhibition with either cyclosporin or Synta 66 resulted in significantly greater maximal inhibition of cytokines than dexamethasone in both peripheral blood and pulmonary CD8 cells [e.g. >95% inhibition of IFNγ (interferon γ) production from pulmonary CD8 cells using cyclosporin and Synta 66 compared with <50% using dexamethasone]. The absolute number of pulmonary CD8 cells co-expressing NFAT1 was significantly raised in lungs from COPD patients compared with controls, but the percentage of CD8 cells co-expressing NFAT1 was similar between COPD patients and controls (80.7% compared with 78.5% respectively, P=0.3). Inhibition of NFAT using the CRAC channel Synta 66 produces greater anti-inflammatory effects on CD8 cells from COPD patients than corticosteroids. NFAT is expressed at a high level in pulmonary CD8 cells in COPD.

Role of the aryl hydrocarbon receptor (AhR) in lung inflammation

Millions of individuals worldwide are afflicted with acute and chronic respiratory diseases, causing temporary and permanent disabilities and even death. Oftentimes, these diseases occur as a result of altered immune responses. The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acts as a regulator of mucosal barrier function and may influence immune responsiveness in the lungs through changes in gene expression, cell-cell adhesion, mucin production, and cytokine expression. This review updates the basic immunobiology of the AhR signaling pathway with regards to inflammatory lung diseases such as asthma, chronic obstructive pulmonary disease, and silicosis following data in rodent models and humans. Finally, we address the therapeutic potential of targeting the AhR in regulating inflammation during acute and chronic respiratory diseases.

Response to add-on inhaled corticosteroids in COPD based on airway hyperresponsiveness to mannitol

BACKGROUND

The use of inhaled corticosteroids in mild to moderate COPD is controversial. The aim of this study was to determine whether airway hyperresponsiveness to mannitol might identify patients who are likely to respond to add-on inhaled corticosteroids.

METHODS

Ninety subjects with mild to moderate COPD were recruited and 68 subsequently randomized in a double-blind manner to receive inhaled budesonide (1,600 μg/d, n = 31) or placebo (n = 37) for 3 months. Thirty-eight subjects had airway hyperresponsiveness to mannitol (17 received budesonide, 21 placebo). All subjects received tiotropium throughout the study, including 4 weeks before randomization. Spirometry, quality of life (St. George Respiratory Questionnaire), degree of dyspnea, airway responsiveness to mannitol, and exhaled nitric oxide were assessed at week 0 (recruitment), week 4 (baseline prior to randomization), and week 16 (posttreatment).

RESULTS

Compared with placebo, budesonide was associated with improved quality of life in subjects showing airway hyperresponsiveness to mannitol (difference of changes in quality of life score between randomization and study completion, −9.1; 95% CI, −15.8 to −2.3; P < .01). Treatment with inhaled budesonide also led to a reduction in airway responsiveness to mannitol compared with placebo (difference in log10 response-dose ratio, −0.3; 95% CI, −0.6 to −0.04; P < .01). However, postrandomization changes in FEV1 % predicted, quality of life, and exhaled nitric oxide showed no difference between budesonide and placebo.

CONCLUSIONS

In subjects with mild to moderate COPD and airway hyperresponsiveness to mannitol, quality of life and airway responsiveness improved after treatment with inhaled corticosteroids added to long-acting bronchodilator therapy.

A new short-term mouse model of chronic obstructive pulmonary disease identifies a role for mast cell tryptase in pathogenesis

BACKGROUND

Cigarette smoke-induced chronic obstructive pulmonary disease (COPD) is a life-threatening inflammatory disorder of the lung. The development of effective therapies for COPD has been hampered by the lack of an animal model that mimics the human disease in a short timeframe.

OBJECTIVES

We sought to create an early-onset mouse model of cigarette smoke-induced COPD that develops the hallmark features of the human condition in a short time-frame. We also sought to use this model to better understand pathogenesis and the roles of macrophages and mast cells (MCs) in patients with COPD.

METHODS

Tightly controlled amounts of cigarette smoke were delivered to the airways of mice, and the development of the pathologic features of COPD was assessed. The roles of macrophages and MC tryptase in pathogenesis were evaluated by using depletion and in vitro studies and MC protease 6-deficient mice.

RESULTS

After just 8 weeks of smoke exposure, wild-type mice had chronic inflammation, mucus hypersecretion, airway remodeling, emphysema, and reduced lung function. These characteristic features of COPD were glucocorticoid resistant and did not spontaneously resolve. Systemic effects on skeletal muscle and the heart and increased susceptibility to respiratory tract infections also were observed. Macrophages and tryptase-expressing MCs were required for the development of COPD. Recombinant MC tryptase induced proinflammatory responses from cultured macrophages.

CONCLUSION

A short-term mouse model of cigarette smoke-induced COPD was developed in which the characteristic features of the disease were induced more rapidly than in existing models. The model can be used to better understand COPD pathogenesis, and we show a requirement for macrophages and tryptase-expressing MCs.

The aryl hydrocarbon receptor modulates acute and late mast cell responses

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor whose activity is modulated by xenobiotics as well as physiological ligands. These compounds may modulate inflammatory responses and contribute to the rising prevalence of allergic diseases observed in industrialized countries. Mast cells (MCs), located within tissues at the boundary of the external environment, represent a potential target of AhR ligands. In this study, we report that murine and human MCs constitutively express AhR, and its activation by the high-affinity ligand 6-formylindolo[3,2-b]carbazole (FICZ) determines a boost in degranulation. On the contrary, repeated exposure to FICZ inhibits MC degranulation. Accordingly, histamine release, in an in vivo passive systemic anaphylactic model, is exacerbated by a single dose and is attenuated by repetitive stimulation of AhR. FICZ-exposed MCs produce reactive oxygen species and IL-6 in response to cAMP-dependent signals. Moreover, AhR-activated MCs produce IL-17, a critical player in chronic inflammation and autoimmunity, suggesting a novel pathway for MC activation in the pathogenesis of these diseases. Indeed, histological analysis of patients with chronic obstructive pulmonary disease revealed an enrichment in AhR/IL-6 and AhR/IL-17 double-positive MCs within bronchial lamina propria. Thus, tissue-resident MCs could translate external chemical challenges through AhR by modulating allergic responses and contributing to the generation of inflammation-related diseases.

Potential significance of telocytes in the pathogenesis of lung diseases

Multiple cells play critical roles in the pathogenesis of lung diseases, even though the exact mechanisms are still not clear. Telocytes are characterized by telopodes, which are thin and long prolongations, and a small amount of cytoplasm rich with mitochondria, as shown by immune-positive staining against CD34, c-kit and vimentin. Telocytes have been found in many organs of mammals, including the trachea and lung. This report summarizes the latest findings associated with telocytes, with a special focus on the lung, and demonstrates that telocytes exist in the smooth muscle layer under cartilage and bronchiole in the lung, and also in the interstitial space of alveoli. Telocytes have a mediate connection with epithelial cells and direct connection with smooth muscle cells both in blood vessels and bronchiole in the lung. Telocytes also have a close relationship with other cell types, such as immune cells and stem cells. Telopodes appear with dichotomous branching and alternation of podom and podomer, forming a 3D network structure with complex homo- and hetero-cellular junctions. All characteristics of telocytes in lung tissue indicate that telocytes may play a potential, but important, role in the pathogenesis of lung diseases.